QA/QC: Quality Assurance and Quality Control

Quality, one of the most important elements in modern industry, has been a challenging and crucial topic for nearly all of the companies that have been existed to serve goods/services. By the definition, quality is considered as “fitness to the application and fulfilling the customer expectation”. It means that it is all about expectations and suitability. Notion of quality solely depends on perception. One may not consider a service high quality whereas the satisfaction of another customer is fulfilled. In most of the cases, the existence of an industrial organization hugely relies on the quality of their service. It is a major concern for every company who are willing to survive in the market for a long period of time. Satisfaction of customers is the most important part of quality management. Therefore, nearly all of the corporative organizations has to have a department for quality management operations. Thanks to the scientific studies, many different methods and systems were developed. This blog post will focus quality assurance (QA) and quality control (QC) processes which fall under the topic of quality management. Seven tools of QC will be explained. But besides those, quality planning will be briefly mentioned. Several methods for quality improvement will also be presented within the content of this post.

Quality Planning

Nothing gets done without a plan of action. Quality planning can be defined as the initial step of quality management where the development of products, systems and processes are done in order to meet customer expectations. Planning step involves defining the customer profile and their needs. Procedures and objectives are in this step.

An example for quality planning: A quality plan is simply a document which specifies the standards, applications, specs and act of plan in sequence. Let’s take a metal parts manufacturer for example. After the standards and specifications have been defined, a sequential inspection process (non-destructive, destructive tests, hands-on inspection etc.) is created. This process makes sure that the fabricated part is satisfactory in terms of standards and specs. Parts fail to complete the quality process are sent to scrap or deburring. This planning operation may contain quality control and quality assurance plans.


Quality assurance and quality control steps form the core of quality management system. These set of processes combined help to ensure service/products and meet the expectations of the customer. These two terms are often used to mention about ensuring the quality of a product, however they are not the same concepts. Quality assurance is the prevention method of possible defects and problems before production of goods and services. According to ISO 9000 standards, this operation is defined as a sub category of quality management process focused on assurance that quality requirements will be met. This mechanism is prior to quality control, aiming to minimize defects and of course loss of time and effort. In essence, quality assurance makes the producer sure about the efforts and precautions taken are in the right path for achieving requested quality levels. Quality control, on the other hand, focuses on the detection of flaws in product. It ensures that created goods/services follows standards and requirements of design. Again, according to ISO 9000, it is defined as a part of quality management used to meet quality requirements. Quality control is a reactive process and it is done after quality assurance. This operation includes many operations within. If we are to give an example from metal fabrication, tensile testing is done for fabricated metal part to identify whether the product meets the requirements in terms of tensile strength.

In order to sum up the main difference of these two concepts, it can be concluded that quality assurance process focuses on preventing while quality control process aims to detect the flaw of created goods and services.

Seven Basic Tools of QC

Developed by Japanese people, seven basic tools of quality help industrial organizations solve complex challenges in quality. This methodology can be applied in any kind of industrial effort, thus widely used. These tools are:

Stratification, based on dividing the existing data into sub categories to derive meaningful information and understand the problem.

Histogram, basically distribute the data as bar graphs to see whether there exists an abnormality or not. By doing this, data may reveal the primal problematics clearly.

Check Sheet, also known as Tally Sheet, helps to see the occurrence pattern of problem by marking checkpoints on tabular form. In some cases, it might even show the causes for problems.

Cause-Effect Diagram (also known as Ishikawa or fishbone diagram), focuses on understanding the root cause of the problem. First, problem is identified. Then a horizontal line is drawn where the other branches of possible roots of defect (machinery, labour, material, measurements, environment, methods) are created. Possible reasons for each branch are written under (For instance, problem can be emerged from machinery due to lack of maintenance). This tool enables much more efficient brainstorming and is the most essential piece of QC.

Pareto Chart, used to point out the most crucial factors that cause the problem. Named after Vilfredo Pareto, it tells us that 80% of problems are caused by 20% of primary factors referred as Vital Few while the rest is called Trivial Many. This instrument helps to set Vital few and Trivial many apart.

Scatter Diagram, is used to check whether the data is positively or negatively correlated. All the data is scattered on a XY plot.

Control Chart, simply a statistical graph used to determine whether data obtained from the process is acceptable within upper and lower limits.

Quality Improvement and QI Methods

Development of quality management systems on the road to serving at higher precision levels by means of desired quality standards has direct correlation with quality improvement. Many engineers, scientists and people from other branches have developed different approaching for quality improvement, all of which are tools for the refinement of processes. Most widely known methods are:

ISO 9004, performance improvement guidelines.

ISO 9001, quality management system. Organizations who are able to meet the demands of this standard can acquire ISO 9001 certification. This certification enables them to show that quality of created goods/services accommodates worldwide known standards. It is the only certified standard.

Taguchi Methods, statistical methods named after Genichi Taguchi, an engineer and statistician. These methods mainly focus on quality improvement based on minimization of amount of experiments needed for prediction of best results.

PDCA, plan, do, check, act cycle used for QC operations.

There exists numerous different methods, however many of them are specialized in certain working areas.


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